Hi from Indiana...my first post as a new member.
I have a 1966 1500. I am starting to tear it all apart and I will be needing some new inner fenders, possibly new grill support and radiator support and other patch panels. My question: is there a difference in the quality of new panels from the suppliers of these parts (LMC, Classic Industries, Auto Metal Direct). Does one of these companies (or even another company) have better quality than any one of the other?
Thanks for your HELP and I am glad I found this site.

Hello Red, Glad you joined. The basic answer is no. No difference. The same Chinese "Peoples Patch Panel Factory" supplies the world . This is true with many other "new" parts. Not all. Just get the best price. I find that the best prices are at Classic trucks of America. 90% of the time you will have to tweak the panels, or the truck, in some way to get a good fit. Remember the rule: only cut out as much as is necessary. Many times you only use a portion of the patch panel. Leave as much of the virgin metal as possible.

I seems you are speaking of two different subjects. New parts and patch panels.
Some of the items you mention are whole parts, not patch panels. When you need a whole part, it is worth the effort to find an original donor part from a GMC or Chevy. They fit better and are cheaper.

Below is: to whom it may concern:

Bit of advice. Take pictures of gaps and how things go together. Keep track of hardware. Reuse the hardware. Chase all internal and external threads. Drill any hinges with two 1/8 holes, spread out a little, thru the hinge and structure, so that you can stick two 1/8 drill bits in holes to place hinged component back in original position if desired. (doors, hood).

I would also advise not doing the "buy everything at once" syndrome (*). Some folks think that's the way to start a project, Wrong! This is why you see so many guys selling their "project" with a crap load of new parts. Work on one area at a time and get those parts as you go. Don't buy any "dress up" parts until finished with the important stuff. Do the rust, dent, patch and prime work first. Try not to scatter parts all over the place. If you do that, after a month or a year, you will think it's too big a job to finish and lose interest.

There are all kinds of reasons that people think one vendor's parts are better. The Chinese part from the same factory has bad quality control. Thus bad batches arrive at various times at various vendors. This can happen on several parts and make us think that vendors parts are worse than another. Our vendors have no control nor can they threaten when there is a single supplier. The vendor is going to buy from the cheapest supplier. That's China. China does not allow competition within. So there is one maker of parts.

Then there is the users truck which was repaired over the 60 year history. Repairs done wrong, out of whack, crooked, and so on. This is then blamed on the "new" part.

Then there is the whacky user who does not know what they are doing, screw up the job and blame the parts. It's a never ending fight and opinionated subject. You just learn to buy from whomever you want and make the part work. Whatever it takes. Vendors would not stay in business if their parts don't fit. Their return policy is a consideration to me also. (*) When you buy parts too far in advance, you may pass the return policy limit by the time you see a problem.